The treatment or processing of such seed materials has been effected heretofore generally in a chain of machines in each of which, one or more separating processes can be carried out so that impurties can be separated from the seed grains and seeds having a poor germinating capability or which are incapable of germination can be removed from those seed grains with the greatest propensity to germination.
Thus it is known in a first step, to carry out e.g. a pneumatic sifting to remove impurities such as straw, chaff and weeds by entrainment in a rising air column under suction from the seed materials and to then subject the seed product to a sifting operation using a variety of types of sieves to separate the seed grains in accordance with grain width and thickness.
Using a winnower or the like, separation is effected based upon length, and thus broken grains, long particles and the like can be separated from the seed product. The final seed separation can be effected in accordance with weight based upon the principle that good seed grains will have a limited range of weights while poor seed grains will have a different weight resulting, for example, from damage or hollows in seed grains. The weight separation can be effected in a fluidized bed utilizing weight-classification principles.
In U.S. Pat. No. 4,490,247, for example, a pneumatic sifter or classifier is provided which affords a separation of a mixture in a heavy and a light fraction utilizing a first oscillating conveyer to convey the material mixture counter to an upwardly directly air stream at the discharge end of the conveyer. A second oscillating conveyer is located at the level of the first or therebelow and the input end of the second conveyer can have an upwardly inclined portion onto which the heavy fraction from the discharge end of the first conveyer falls. The heavy fraction is thereby separated from the light fraction which is carried off by the air stream over the horizontal measure part of the second conveyer.
In U.S. Pat. No. 4,219,410, a method and apparatus for separating heavy metal particles from lighter chips are described. The chips which surround the heavy metal articles are moved along a conveyer path over a slit transverse to the conveyer direction. A gas stream is directed through the transverse slit to entrain the chips away form the heavy metal particles which fall through the slit.
Europatent publication No. 126 177 describes an apparatus for sorting granular products utilizing a column arrangement which is subdivided by sieves of different mesh size. A device is provided for generating an artificial airflow through the column so that the product to be sorted is entrained by the air stream through the sieves and is thus separated by size.